The present invention relates to improved apparatus for the combining of foreground and background scenes for motion picture or television purposes, and particularly relates to the so-called "blue-screen" or special background color screen systems.
My prior U.S. Pat. No. 4,100,569, granted July 11, 1978, discloses an electronic circuit for combining foreground and background pictures substantially linearly, and included special arrangements for accommodating objects including both blue and magenta colors in the foreground. The system as described in the above-identified patent has outstanding characteristics in the merging of foreground and background pictures through a wide range of transparency of the foreground objects. In addition to the normal type of transparent foreground images, including smoke, glasses, and the like, the edges of moving objects should also be shown as being partially transparent to provide the proper illusion of rapid movement. However, certain problems have been encountered in the everyday usage of the prior system, and some of these problems are enumerated below:
One problem has been caused by black glossy objects in the foreground scene. More specifically, these dark glossy objects tend to reflect the backing color (normally blue) and therefore fail to "matte" or fail to become opaque in the composite picture, with the result that some portion of the background color "prints through" in this area of the composite picture. In certain other cases where the foreground picture requires back-lighting, for example, the glare produces shadow inversion and high levels of noise. Another important problem involves scuff marks and footprints on the blue floor forming part of the foreground scene and which has caused undesired effects on the composite photograph.
It is often desired to have special shadow effects in a moving picture, and either have shadows intensified, or substantially eliminated. In my prior U.S. Pat. No. 4,100,569 mentioned above, the shadow controls were relatively complex, and it proved to be somewhat difficult to learn how to effectively manipulate them. Accordingly, it would be desirable to have a single control knob for shadow effects. Other special conditions which require special handling include black backgrounds and white backgrounds. In the case of black backgrounds, the prior circuitry was unable to effectively handle partial transparency situations; and in the case of cartoons, instead of using a simple white paper background for the cartoons, it has previously been necessary to prepare the cartoons on transparent sheets, and this is more difficult and time-consuming than preparing cartoons on conventional white paper.
The principal object of the present invention is to provide an improved comprehensive compositing system which effectively solves or eliminates the problems and provides the additional capabilities outlined hereinabove, in an effective and relatively simple manner.